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The Quest for Supporting Snapshot Isolation in Transactional Memory
{ Wed, 12 Mar 2014, 14h30 }

By: Ricardo Dias

Transactional memory (TM) eases the burden of correctly synchronizing concurrent programs by using a model similar to coarse-grain locking. However, in contrast with coarse-grain locking TM allows the program to scale in throughput with the increase of execution threads. Traditional TM systems rely on optimistic concurrency control techniques to guarantee a Serializable model of execution, i.e., the concurrent execution of a set of transactions is equivalent to some sequential execution of the same set of transactions.

The efficiency of TM systems depends directly on the conflict rate generated by the application, and to guarantee serializability, TM systems must conservatively detect all read-write conflicts between transactions. As a consequence, some transactions that would not violate program’s correctness are unnecessarily aborted, thus causing a slowdown in the overall throughput of the system. Snapshot Isolation based TM systems enable concurrent access to shared data without aborting on read-write conflicts. Unfortunately, Snapshot Isolation does not provide Serializability as it permits certain anomalies which can lead to subtle consistency violations.

In this talk, I will discuss recent work which main objective is to support a snapshot isolation runtime while preserving serializability as the correctness model for memory transactions. I will present a brief survey on the state-of-the-art techniques that identify serialization anomalies caused by snapshot isolation execution, and also discuss recent work we have conducted that focus on the correction of anomalies before the program execution.

Hosted by: Computer Systems

Location: DI seminars room

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